Radio receiving set



Oct. 24, 1933. s w SEELEY RADIO RECEIVING SET Filed April 25, 1931 WM W Patented Oct. 24, 1933 UNITED STATES mmo RECEIVING ,SET

Stuart w. Seeley, Jackson, Mich, assignor, by mesne assignments, to Radio Corporationof America, New York, N. Y., a corporation of Delaware Application April 23, 1931. Serial No. 532,208

'11 Claims (Cl. 250) Other objects of the invention will appear in the following description, reference being had to the drawing in which thesinglefigure is a diagrammatic illustration of the circuits of the apparatus in which the invention is embodied.

Referring to the drawing, 1, indicates the an- ,tenna connected through variable condenser 2 and an impedance coil 3 to the ground at .4. The grid of an amplifying tubeya four electrode or screen'grid tube 5 being shown, is connected to the impedance coil at 16 and a cathode 'lwhich is preferably of the uni-potential type, is connected through inductance 8 and grid resistance 9 to' the other end of impedance .coil 3. This places the potential of the incoming signal be-. tween the grid and the cathode. The screengrid 10 of this tube is placed between the other .grid and the plate 11 in a well known way and .is connected through; resistance 12 to an intermediate positive terminal of the power supply, for example, the 90 voltterminal. The plate 11' of tube -5 is connected through the primary 13 of the radio frequency transformer and thence to one coil '14 of the 60 cycle transformer, control resistance 15, contact 16 on the changeover switch, and when. this is thrown into the lower or standby position, the circuit is completed through the switch to contact 17, conductor 18 to a plate supply, for example, 180 volt terminal l9. Thegrid of tubes 20, 21, 22 and 23 are all connected through their corresponding coils 24, 25, 26 and 2'7 to the ground 4, and the plates 28 and 29 are connected through coils 30 and 31 in parallel with the plate 11 to the coil .14 I of the 60 cycle transformer previously referred to'when the switch is thrown into the standby position. When the switch is thrown into the vertical position so that contact is :made between points 32 and 17 all of the plates 11, 28and 29 are connected through wire 33, volume control resistance 34, contacts 32 and 1? and wire 18 to the same 180 volt terminal. In this position of the switch the coil 14 is not energized. ,The screen grids 35 and-36 are connected through their corresponding resistances 3 8, 39 with the same potential terminal as screen grid 10.

The plate 40 'of tube 22 is connectedthrough a radio frequency choke coil: 41, transformer coil 42, to the plate terminal 19 above referred to.

The plate 43 of tube 23 is connected through wires 44, 45, with transformer 46, junction pointv 46', .wire 47, inductancecoil 48 to the mid point of transformer coil 49 that energizes the filament 50 0f the rectifying tube 51. tential cathodes 52, 53 of the tubes 20, 21 are connected respectively through individual inductances 8 and a common resistance '9 .to the ground point 4. The unipotential cathode 54 of tube 22 is connected through individual grid bias resistance 55 to the ground point 4, All of the screen grid tubes have radio frequency bypass condensers 56, 57, 58 .between ground 4 and the unipotential cathodes, screen grids and plates respectively. Radio frequency bypass Icondensers 59, 60 are bridged in series across the choke coil 41 and a connection is made from ground 4 through condensers :61, 62 to a point midway between said condensers 59, 60. The unipotential cathode 54 of the tube 22 .is also connected by line 63'with this midpoint. Condensers 56, 61 and 62 bypass the radiofrequency in the electron flow between plate and cathode to prevent a radio frequency potential 'in the grid bias resistance 9 and 55. This eliminates the feed back between the plate andfgrid lof each tube that would otherwise occur to .produce degeneration.

The condensers 5.7, 58 bypass .the radio .frequency around the voltage supply to the screen grids andplates respectively. The condensers 59 .and- 60 together with condensers 62 and .61 bypass the radio frequency around the transformer coil 42. i a

The power supply is obtained from the usual alternating current means by inserting plug 64 into a receptacle connected to suchsource, of supply. When switch .65 is closed alternating current passesfrom lead 66 through transformer coil 67 and any one of theadjustment taps to wire 67, wire 69, switch 65, wires 69 and '69" throughthe fuse back to .the plug. This induces alternating current in coil 49 used toheat the filament 'of the rectifier, coil '68, to furnish the alternating current to be rectified and coil '70 to furnish current for the filaments 71, 72, 73.; 74, and '75. Filaments 71 and 72 on the one hand and filaments '73 and '74 on'the other, are placed in series acrossthe transformer coil 70.

When power switch .65 is closed filament .50 will be heated by the current from ,coil .49 and the unipotential cathodes 7, 52and 53 and 54 will be heated by filaments '71, 72, 73 and 74 respectively. Filament cathode 75 will be ener gized directly by connection to coil 70.

Current in one cycle of the alternations of the ,power supply will pass from filament 5,0 of .the rectifier 51 to plate '76, transformer 68,

The unipoground 77, ground '78, resistances. 79 and 89, lines 81,-82, loud speaker field coil 83, wire-47, inductance coil 48, mid tap connectionof transformer 49 back to the filament. This rectified current therefore passes in series through the resistances 79 and 80 and the field coil 83. Dur

ing the other .cycle of the alternating "current the current will flow from filament. 50 of the rectifier tube to plate 84 through the'opposite terminal of transformer 68 to ground 7'7 and thence through the same circuit in the same direction thus furnishing double wave rectification. The 90 volt terminal of screen grids 10,

and 36 are connected between the resistance 79' and 80 to give an intermediate potential say 90 volts, while the plates 11, 28, 29, and-- are connected to the high potential end of resistance to obtain the highest potentiaL'for' example, 1'80 v01ts. I

Coil 46 is coupled to coil which is in circuit with movable coil 560i the loud speaker. One

' terminal'jof coil 85 is connected to contact 8? of the standby-receiver switch, the other terminal being connected directly to coil 86. The other terminal of coil 85 is connected-through wire 80 to. plugtip contact 89: Thering contact 90 of this plug connection'is connected'to con-- tact 91 on the switch above referred'to. The alternating current line 66 connected to plug 64 is joined by wire 92. with' coil 93 coupled-to coil 14. The other'end of coil 931s connected through wires 94 ands?- to the other terminal of thepower supply transformer 6'7. 'The pur pose of this last mentioned circuit will be explained'in detail later.

Signal device 95 adapted to be operated by a 60'cycle current modulation is connected across transformer secondary 96 which is coupled to ,7 the primary 9 7. One terminaljof this primary isiconn'ected through a large condenser '98 with natin'g current supply. The terminals of traine former ,70 are also shunted by twocondensers 1,09 and placed inseries thereacross and the point between these two condensers is grounded at 111. Thesefcondensers act as aradio frequency'bypass. Condenser 112 is ccnnectedto ground at 113 and likewise serves as a radio frequency bypass condenser. I

The electron flow between cathodes 7, 52 and 53 of tubes 5,20 and 21 must'pass to "the corresponding, plates through the rectified power supply, ground 4 and grid bias resistor This places the cathodes a'ta positivepotential inrespectjto' the grids of these tubes. In other words, these grids are'negative in respectto cathode and get their negative biasin this way; The'electron 'flowbetween cathode 54 and plate 40 of tube 22 must pass from the plate supply in theway. previously traced through resistance 55. Therefore'the grid of tube 22 is negatively biased with. respect to this cathode by this re si'stance. The'. electron flow from cathode '75 to plate 43' of tube 23 must pass from ground The operation of the receiving set will now be described:

Let it be assumed that this receiving set is installed. in the station of a police or other peace force and that no attendant is hired to stay in the immediate vicinity of the receiving set. The standby-receive switch would be thrown into down position of the drawings and when no signal. is coming in the 60 cycle current that is continually passing through coil 93 produces a 60 cycle alternating voltage ripple in the plate supply-of tubes 5, 20 and 21 butthis "does not afiectthe' current in the plate of tube 22 lee-- cause of the loosecoupling between coils 31 and. .26. Therefore there is no alternating current" sent through the coil 46 of the alarm trans-' former. At least the amount of alternating cur-- rent in this circuit is insufficient to ring the alarm. When the signal, that is, thetelephone message, broadcast to all of the police stations reachesthe antenna 1 radio frequency currents will pass through the tubes in well known ways that heed not be'specifically described and radio frequency currents to plates 11, 28 and 29 of tubes 5, 20 and 21 will be modulated bythe ripple voltage in' the plate supply and the modulated radio-frequency'current will be introducedinto the grid circuit 26 of the tube 22 where itwill be detected in the usual manner andthe 60 cycle modulation passed into the tube circuit 27 of the final tube 23. The plate current of this latter tube will then pass through wire 44 to point 99, wire 45, coil 46, wire 47 to 'the'filter inductance 48, coil 49, filament 50, plate '76 or 84 to ground '77, ground 105, lead '75 and the filament of tube 23 back to the plate 43.; This circuit includes the rectifier 51 and the filtering device 48 which furnishes the plate supply.

The coil 97 is connected to binding post 99 through condenser 98 and wire 100, and by contacts 101, 102, grid bias resistance 104, ground.

105 toground 77 on the power supply. As has just been explained the plate current modulated by 60 cycle current of tube 23 passes in the circuit between the mid top of filament trans former 70 and binding post 99 across which coil 9'7is,connected. The potential drop across these points, which has 60 cycle modulations will there fore beimpressed on coil 97 and be introduced into the secondary 96 which is connected directlytothe alarm gong95. The 60 cycle current will cause this gong to produce a loud noise that can be heard by anyone in neighboring rooms and they can immediately go to the room having the radioset if they are not already-there and throw the standby-receive switch to the up position asshown in the drawing. This will disconnect the alarm gong and the 60 cycle current formerly introduced into the circuit'through the transformer coil 93 and it willconnect the plate circuit of tubes 5, 20'and 21 through wire 33, volume control resistance 34, contacts 32 and 1'7 to the 180 volt potential binding p'ost19. The

plate circuit of tube 23 will pass through the same circuit as previously described which includes loudspeaker coil 46. However, this loud speaker connection will now become effective becausethe circuitof the transformer 85 heretofore open will now be closed by connecting the contacts 91 and 87 of the switch.

The telephone message will therefore pass in regular order through all of the tubes and into the loud speaker and it will be received by all the police stations having the equipment. After the message has been received the switch can be thrown into the down position ready for the next alarm signal which will come in as soon as another message reaches the antenna.

The telephone jack 89, 90, is for the purpose of inserting a telephone head set or signal receiving device in place of the loud speaker.

While I have described the use of the invention particularly in connection with peace ofiicers in crime prevention work, it of course will be readily apparent that the system can be employed in any other use where it is desirable to use an alarm or equivalent signalling device to call attention to the fact that a signal is being received.

Various modifications may be made in the radio circuit connections without departing from the spirit of the invention and the antenna is not to be limited to the particular arrangement disclosed which has been by way of example only.

I claim:

1. In sets for receiving radio signals, means for receiving communication signals, a coil connected to said means adapted to receive the said signals therefrom, a second coil coupled to said first coil, a potential source connected to apply alternating voltages to the first coil having a frequency quency incapable of inducing a substantial potential in the second coil through the coupling between the two coils, means for producing a call signal, means for producing a communication signal and means for connecting either of said two first mentioned means to the second coil.

3. In sets for receiving radio signals, a vacuum tube having a grid and a plate circuit, a coil connected in the grid circuit, a second coil loosely coupled to said first mentioned coil, a source of audio frequency potential in circuit with said second coil and means containing a call-signal device connected to receive potentials in said plate cirmodulated current and not audio frequency curcuit.

'4. In sets for receiving radio signals, a vacuum tube having input and output circuits, coupling means in said input circuit for introducing radio frequency energy thereinto, an audio frequency source of potential connected to said coupling means but incapable of inducing in the said input circuit substantial potential through said coupling means and a call signal device connected to said output circuit. 7 I

5.1m sets for receiving radio signals, a vacuum tube having input and output circuits a coil in the input circuit, a second coil loosely coupled to the said coil, an audio frequency source of potential in circuit with said second coil but incapable of inducing a substantial potential in said circuit, means for introducing a radio frequency signal into the second coil, a telephone receiver, a call signal device connected to said output circuit and means to disconnect the call signal device and to connect the telephone receiver thereto.

In sets for receiving radio signals, a vacuum tube having grid and plate circuits, a coil connected in the plate circuit, a coil loosely coupled to the first mentioned coil, an audio frequency source of potential connected to said first coil incapable of inducing a substantial potential in the second coil but capable of modulating a radio frequency signal in the first coil, a telephone receiver and a call signal device and means to alternatively connect the receiver and the signal device tothe first mentioned coil.

7. In sets for receiving radio signals, a signal receiving circuit, a radio relay having a radio frequency coupling to said circuit, a source of audio frequency potential connected to said circuit, signal reproducing means connected to said relay and means to disconnect said source of audio frequency from said circuit to reproduce a message.

8. In sets for receiving radio signals, a vacuum tube having input and output circuits, a coil having aradio frequency coupling with the input circuit, an antenna connected to said coil, a sup ply source adapted to produce an audio potential in said coil, means adapted to reproduce call and message signals introduced into said plate circuit 7 and means to disconnect said source from said 105 coil to receive the signal.

9. In sets for receiving radio signals, a vacuum tube having grid and plate circuits, a coil connectedin the grid circuit, a second coil loosely coupled to the first coil, a source of audio frequency potential connected in circuit with the second coil during the stand-by period, the flux produced by said audio frequency potential being incapable of passing alone across said coupling, means tointroduce a radio frequency signal into the circuit of the second coil to interact with the audio potential frequency to produce a flux capable of passing across said coupling, a call signal device connected to said plate circuit and adapted .to be energizedby currents produced by the reaction of said audio and radio frequencies, a loud speaker, and means to disconnect said source of audio frequency potential from said second coil and to connect said loud speaker to said plate circuit to reproduce the signal.

10. In radio call systems, a circuit adapted to receive high frequency current, a source of audio frequency current adapted to modulate the'high frequency current in said circuit, another circuit loosely coupled to the first circuit for receiving 130 rent, a call signal device connected to the second circuit, means to disconnect the said source from the first circuit and a communication signal device connected to the second circuit.

11. In radio call systems, a circuit adapted to receive high frequency current, a source of audio frequency current adapted to modulate the high frequency current in said circuit, a rectifier loosely coupled to said circuit for passing modulated high frequency current but not audio frequency current, a call signal device connected to said rectifier responsive to the rectified modulated current, means to disconnect said source from said circuit and a communication signal device adapt- I ed to be connected to the said rectifier.

STUART W. SEELEY. 

